The placeholder text for new MCQ choices should either not be there or be selected when you click the content area

[christianp]

When you add a choice to a multiple-choice part, its text is initially something of the form "Choice N". You have to select this and delete it before you can write the text you want.

I think the easiest way to resolve this is for the field to be empty.

In editor/static/js/question/part_types.js, change the addChoice method so the content observable is initially the empty string ''. There are corresponding methods for the m_n_2 and m_n_x part types also in that file.